Your knives will never be sharper when using the new combination sharpening stones from Mercer Cutlery. The Starter Stone has coarser grit levels to repair damaged edges or for blunt knives. The Finishing Stone is made with finer grit levels for eliminating burrs on the knife blade edge. The stones are made from high quality corundum. Silicone base holder included with each stone to create a non-skid surface, prevent damage to work surfaces, and protect the stone.